Cam Core Dia for Big Lift

Q: What cam bore diameter can us Mopar folks run in a Calaise block? What is the next step up from stock, and when do you need one? How much cost to a cam does it add?

Based on comments made in previous posts, 60mm cores for Hemi engines are pretty common. The Fuel guys run them.

What do you consider to be "big" in regards to lobe lift?

I have an older SS block that is machined for a 2.500" cam tunnel bore, Ford 2.125" cam journals. Ford Performance sells the five roller bearings at a good price. The stock front journal is about 50mm, so 55mm or 60mm are the next steps up in roller bearings after the BBF journal size. I'd check on availability and prices on cams before machining the block.

I've read both 55MM and 60 MM cam cores and bearings being use for all out BB after market race blocks
As already ask how much lift do you want to use? What rocker arm ratio?
Lots of way to make things happen your way

I am just curious....I am at .750 lift now on the street/strip car, and wondering how the cam & bearings are holding up. Lots of spring pressure already, and I know guys are running .800" lift on the street these days. The only way I can imagine that is with a thicker cam core...I may have answered my own question there, but I am curious what others have done. I want to make this car somthing I could take on Drag Week. So when I look at cams next time, I want to be able to figure out if I need to go to a 55mm or 60mm core or maybe stay where I am at.

A coated cam bearing, and using a heavier weight oil will be your best bet for a Drag Week combo. Oil temp, and valve spring cooling is the key to surviving Drag Week. Also using bushed components, instead of needle bearings is another DW must use type deal. making a car work on the track is completely different than one that needs to drive 250-300 miles per day. The drives take out more cars, then the track.

I like the Durabond coated cam bearings.

I was advised not to exceed .500 lobe lift and 900psi open spring pressure on a stock journal size cam core.

Something about the base circle getting small IIRC?

What are the first sogns of camshaft flex? Would you see it in the bearings first?

I run a .730ish lift solid roller with a heavy spring on my small block. A recent inspection after 5 years revealed my cam bearings looked horrible. 3 drag weeks, 150-200 passes, and 5000-7000 miles maybe? I just went back with standard but will likely have this engine apart again before 5 years.

Yeah, that is what I am afraid of....No good way to inspect them either....I put 2000 miles on mine last summer, and zero so far this year, but...

Whats big lift? As mentioned 55 and 60MM are pretty common. If it is a wedge much harder to come by at times. Hemi/Predator stuff much asier to find as the blown alky guys use the bigger cores. IMO most any cam selection over .800 will greatly benefit from a larger than stock core, there is a surprising amount of flex with BIG lift cams and the normal big lift springs they require. Getting the block machined would be your next issues. But Weston Machine can handle it and do it right and he's in NJ so not that far away for you.

I figured its probably about .800 valve lift. like you're saying...If I redo this engine this winter, I was wondering if i should open up the bores and get a nice big bore, tight lash cam that is Drag Week friendly and yet makes the HP...Not sure if that is possible....But one of the reasons you don't see these engines on Drag Week is the valve train....Might be ok at car cruises, and some weekend flogging, but not 1400 miles and then more flogging...Never gonna happen.

I should just put a Hellcrate in the damn car and start enjoying it...one of these years.

What spring pressures are you running? 260-280 on the base and 700-740 on the nose (open)?

Shimmed like I have them they are probably 250 on the seat, not sure what open is but I doubt it is as high as you mention. I lose a lot of lift due to the 59* lifter angle and the offset intake pushrod so they are shimmed up a fair amount to be .050-.060 from coil bind. These springs did two drag weeks and still checked out within spec on seat pressure, did a third with them and retired them for a larger cam and the comp 955 spring that is a little heavier.

100% Al, couldn't agree more. FWIW I just finished a block that i had 55mm cam core done with needle bearings. I had bullet make me a 55mm cam and we used a jessel key way lifter that uses a bushing instead of needle bearings. after it was machine, there was a couple places that had less the .200 of material left.

I currently run a stock cam core, .868 gross lift, .510 lobe lift, stainless valves, 7500 rpm max. Flex when checking lash showed an increase of . 005 to . 006 in lash around the base circle from flex and compression. I would love to see a spintron video of what is going on at 7500 rpm! A move to a bigger cam core, higher rocker ratios and Ti valves is all in the interest of a better race valvetrain.

I have a 55MM camshaft with roller cam bearings and over .800 lift in my street/strip Hemi.

How many street miles on it? Are you ever afraid of the roller bearings finding their way into somthing else?

Are your rocker arms on a single shaft or are they a paired shaft set up?
I'm thinking single shafts systems flex, especially on motors with high (250Lb+ on the seat with 700+ lbs. open) valve spring pressures

Over 5 years and thousands of miles. So far so good.

Your example is perfect showing not all parts respond and perform the same
What brand did you buy and use?
Did you have the rear cam bearing enlarge also for the 55MM or leave it stock and use a stock Babbit type rear stock bearing their?

We see over .040" of lost lift at the valve from deflection even with a 60MM cam, individual steel rockers and single shafts(two bolts per rocker three per stand) with as big a pushrod as we can squeeze in it on the SBC in the Vette. Point is deflection is always there and the bigger core helps. Be great if we could get a 9 cam bearing block that also helps a ton. But only going to find that in a couple applications. We have planned to go to a clamshell bearing so we can go to a bigger lobe to gain the lift we think we need to compete in NA10.5 given the deflection losses we see. We simply cannot put a bigger lobe on the cam now and clear the 60MM bearing..Point is deflection is a real thing, the bigger the stick the ore of it you will encounter.

Are you asking me? Yes, all of my journals are 55MM roller bearing with an enlarged cam plug register also.

I think once you start getting near 0.500" of lobe lift, going up to a larger core is a must. If you are paying for a custom core, plus enlarging the tunnel, it wouldn't make sense to not go up to 60 mm. There is a conversion babbit bearing that allows the use of a 65 mm core in a roller 60 mm tunnel as well. Or go up again using clamshell bearings, which gets spendy.